1. Field of the Invention
The invention relates to bearings for a shaft of a motor. More particularly, this invention relates to bearings having at least one reservoir to store a lubricant for lubricating a shaft of a motor.
2. Description of Related Art
Various bearings have been developed for lubricating a shaft of an electric motor. Sintered metal bearings are the most common type of bearings utilized for this purpose and are well known in the art. Such sintered bearings are generally formed from a porous metal, which is impregnated with a lubricant such as oil, to lubricate the shaft. An example of a conventional oil-impregnated sintered bearing is disclosed in U.S. Pat. No. 6,505,971.
To ensure a longer service life for the bearing, added oil storage is provided by placing an additional lubricant in a cavity around a conventional oil-impregnated sintered bearing. A bearing device in accordance with the prior art is shown in FIG. 1 which includes an oil-impregnated sintered bearing 10 held in place within an end shield 12 by a spring retainer 14. The bearing 10 includes an outer surface 16 and an inner surface 18 defining a bore for receiving a rotatable motor shaft (not shown). An additional lubricant 20 is deposited in a cavity 22 formed in the end shield 12 around the outer surface 16 of the bearing 10 and is absorbed into the bearing 10 through capillary action and delivered to the inner surface 18 for lubricating the motor shaft extending therethrough.
U.S. Pat. No. 2,706,693 discloses another type of oil-impregnated sintered bearing having a reservoir or cavity formed within a bearing body for filling or charging with a lubricant. This may be done by immersing the bearing body in a hot bath of oil, especially one which is boiling. It may also be done by immersing the bearing body in a heated oil bath in a vacuum tank from which the air has been removed by an air pump, causing the air and other gases to be drawn out of the reservoir through the pores of the bearing body. A still further method of charging the reservoir with lubricant is to place it in a cylinder containing a thin grease or oil and applying pressure upon a piston to force the grease or oil through the pores of the bearing into the reservoir or cavity. An inherent drawback with this type of bearing is the complicated and inefficient process of filling the internal reservoir.
To overcome the difficulty of filling an internal reservoir such as that described above, U.S. Pat. No. 3,953,089 discloses a sintered bearing having a cylindrical body provided with three passages or reservoirs equi-angularly spaced and extending fully through the body. The reservoirs may be filled with a suitable lubricant to provide a relatively large reserve of lubricant which over an extended period of time will percolate through the pores in the bearing body to lubricate a shaft and which will be effective to maintain proper lubrication of the bearing for an extended period of service. It will be appreciated that the process of filling each reservoir with lubricant is simplified due to having unrestricted access to each end of the reservoir through which the lubricant may be introduced or injected.
To reduce costs and cut down on inefficiencies, automated processes are being employed to fill the reservoirs or cavities in the bearings with lubricant. Consequently, it is desirable to provide an improved bearing having one or more reservoirs formed specifically for receiving a lubricant using an automated process.